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Bacterial resistance has become a serious public health problem in recent years, thus encouraging the search for new antimicrobial agents. Here, we report an antimicrobial peptide (AMP), called PEPAD, which was designed based on an encrypted peptide from a Kunitz-type plant peptidase inhibitor. PEPAD was capable of rapidly inhibiting and eliminating numerous bacterial species at micromolar concentrations (from 4μM to 10 μM), with direct membrane activity. It was also observed that the peptide can act synergistically with ciprofloxacin and showed no toxicity in the G. mellonella in vivo assay. Circular dichroism assays revealed that the peptide's secondary structure adopts different scaffolds depending on the environment in which it is inserted. In lipids mimicking bacterial cell membranes, PEPAD adopts a more stable α-helical structure, which is consistent with its membrane-associated mechanism of action. When in contact with lipids mimicking mammalian cells, PEPAD adopts a disordered structure, losing its function and suggesting cellular selectivity. Therefore, these findings make PEPAD a promising candidate for future antimicrobial therapies with low toxicity to the host. • PEPAD is an encrypted peptide of the sequence of ApTI. • PEPAD is a peptide with an α-helix secondary structure. • PEPAD has safe use on Galleria mellonella larvae, PBMC and erythrocytes. • PEPAD exhibited potent antibacterial activity against various bacterial strains. • PEPAD's mechanism of action against planktonic cells targets the membrane directly. [ABSTRACT FROM AUTHOR]

Antimicrobial peptides (AMPs) are a current solution to combat antibiotic resistance, but they have limitations, including their expensive production process and the induction of cytotoxic effects. We have developed novel AMP candidate (peptide 3.1) based on indolicidin, among the shortest naturally occurring AMP. The antimicrobial activity of this peptide is demonstrated by the minimum inhibitory concentration, while the hemolysis tests and MTT assay indicate its low cytotoxicity. In optical diffraction tomography, red blood cells treated with peptide 3.1 showed no discernible effects, in contrast to indolicidin. However, peptide 3.1 did induce cell lysis in E. coli, leading to a reduced potential for the development of antibiotic resistance. To investigate the mechanism underlying membrane selectivity, the structure of peptide 3.1 was analyzed using nuclear magnetic resonance spectroscopy and molecular dynamics simulations. Peptide 3.1 is structured with an increased distinction between hydrophobic and charged residues and remained in close proximity to the eukaryotic membrane. On the other hand, peptide 3.1 exhibited a disordered conformation when approaching the prokaryotic membrane, similar to indolicidin, leading to its penetration into the membrane. Consequently, it appears that the amphipathicity and structural rigidity of peptide 3.1 contribute to its membrane selectivity. In conclusion, this study may lead to the development of Peptide 3.1, a promising commercial candidate based on its low cost to produce and low cytotoxicity. We have also shed light on the mechanism of action of AMP, which exhibits selective toxicity to bacteria while not damaging eukaryotic cells. [ABSTRACT FROM AUTHOR]

The present work deals with the fabrication of cost-efficient nanocomposite proton exchange membrane (PEM), prepared by incorporation of nanoparticles of Fly Ash (FA) collected from M/s Bina thermal power plant Madhya Pradesh India; within the host PVDF [poly(vinylidene fluoride)] polymer matrix. Subsequently, the nanocomposite membranes are treated with the well-known sulfonating agent chlorosulfonic acid at 60˚C for 1.5 h. The successful incorporation of FA nanoparticles within the host polymer structure along with the sulfonation of the nanocomposite membranes was confirmed by using FTIR, XRD, FESEM-EDX, and AFM studies. The ion exchange capacity (IEC) and proton conductivity (PC) of nanocomposite membranes are observed to be 0.58 meq g−1 and 3.30 × 10−2 S cm−1 respectively. Further, it was interesting to note that the fabricated membranes exhibited enhanced water uptake capacity up to 19.6% with supressed methanol crossover (1.7 × 10−7cm2/s). Among all the fabricated membranes, the membrane SPF-5 (containing 5% w/w FA), exhibited significantly high membrane selectivity 1.94 × 105 Scm−3 s over corresponding Nafion-117 (2.47 × 104 Scm−3 s), which clearly indicates its potency towards an alternative to costly Nafion-117 for DMFCs (direct methanol fuel cells) application. [ABSTRACT FROM AUTHOR]

The aim of this study is to utilize the electromembrane extraction (EME) system as a manner for effective removal of zinc from aqueous solutions. A novel and distinctive electrochemical cell design was adopted consisting of two glass chambers, a supported liquid membrane (SLM) housing a polypropylene flat membrane infused with 1-octanol and a carrier. Two electrodes were used, a graphite as anode and a stainless steel as cathode. A comprehensive examination of several influential factors including the choice of carrier, the applied voltage magnitude, the initial pH of the donor solution, and the initial concentration of zinc was performed, all in a concerted effort to ascertain their respective impacts on the efficiency of zinc elimination. Two distinct carriers, namely tris(2-ethylhexyl) phosphate (TEHP) and bis(2-ethylhexyl) phosphate (DEHP) were evaluated, in a tandem with utilization of 1-octanol. The results revealed essential role played by the applied voltage in augmenting the rate of mass transfer of zinc across the membrane. The best operating conditions were utilized for 1-octanol enriched with 1.0 vol.% bis(2-ethylhexyl) phosphate as a carrier, applied voltage of 60 V, initial pH of 5, initial zinc concentration of 15 mg L-1, extraction duration of 6 hours, and stirring rate of 1000 rpm. Surprisingly, operating under these meticulously devised conditions culminated in the outstanding removal efficiency of 87.3 %. In comparison with no applied voltage, a substantial enhancement in removal efficiency was observed, trans­cending from a meager 36.67 % to an impressive 87.3 % at 60 V, suggesting thus a tremen­dous potential of EME as an efficacious technique for the elimination of heavy metals.

Remarkable progress has been made to develop proton exchange membrane for direct methanol fuel cell to achieve higher power density. However, the higher methanol cross-over and poor water management are the two major obstacles of fuel cell which significantly reduces its performance. In this work, we have developed a highly performance Ionic Liquid (IL) modified chitosan based composite membrane and characterized by different experimental technique. The incorporation of IL in the chitosan composite introduces cationic acid which increases the ion exchange capacity and proton conductivity. Although the hydrophilic base of IL enhances water uptake capacity of the composite, the water is strongly attached with the polymer chain via hydrogen bonding thereby reducing free water content. The incorporation of Carbon Nanotubes (CNT) and bulky pendant group of IL in the chitosan composite reduces methanol cross-over and the methanol cross-over reported for CPCN@IL-4 composite (5.58 × 10–8 cm2sec−1) is significantly lower than the commercial N117 membrane (2.74 × 10–6 cm2sec−1). The IL modified composite membrane provides higher proton conductivity and membrane selectivity which is desirable for fuel cell design. At 70 °C, the maximum proton conductivity was achieved in CPCN@IL-3 composite (21.52 × 10–4 Scm−1) and the proton transport was controlled by bound water regulated Grotthus mechanism. The polarization curve obtained for CPCN@IL-3 composite at 70 °C and 2 M methanol feed in a single cell of fuel cell provides the maximum power density of 82 mW/cm2 at a current density of 370 mA/cm2. The modification of chitosan based composite membrane with CNT and IL significantly reduces the methanol cross-over and provides higher membrane selectivity which will attracted a possible candidate for DMFC application. [ABSTRACT FROM AUTHOR]

The issues associated with the operation of reverse osmosis plants at the water intake facilities (WIF) for the treatment of drinking water from groundwater sources are described. Ways of increasing reverse osmosis plants performance are considered. The technology of plants modernisation with the purpose of operational costs reduction and minimisation of concentrate discharges into sewerage system, consisting in replacement of reverse osmosis (RO) membranes with nanofiltration membranes, is provided. The use of nanofiltration membranes reduces the intensity of sedimentation and at the same time the concentrate flow without the sedimentation hazard. Also, nanofiltration membranes make it possible to reduce inhibitor dosage and operation costs respectively. Experimental studies on groundwater treatment and efficiency of the provided technology have been carried out. Rates of sedimentation in each device of the layout, as well as composition of water treated by each device depending on the volume reduction factor K (source water flow to the concentrate flow ratio) for the plant were determined. The feasibility comparative study considered the following parameters of the plant operation, without limitation: inhibitor dosage, membrane types, salt selectivity of membranes, source water volume reduction factor K.

Current commercial nanofiltration and reverse osmosis membranes are limited in scope and performance due to their physicochemical properties. Desalination of hydraulic fracturing wastewater poses a particular challenge to membrane filtration given the high concentrations of both organic compounds and salts present in these waters. The recently-developed nanoporous, bicontinuous cubic, lyotropic liquid crystal, thin-film-composite polymer membrane (TFC QI membrane), having unique physicochemical properties, enables an alternative treatment of hydraulic fracturing wastewater. Specifically, the TFC QI membrane recovers the organic compounds from this high-salinity wastewater, enabling biodegradation to occur after desalination. However, other performance criteria must be demonstrated for a membrane to reach application. The work presented herein demonstrates the stable performance of the TFC QI membrane during 66 h of cross-flow filtration of hydraulic fracturing produced water. Compared to the commercial NF90 membrane, the TFC QI membrane recovered a larger portion of the organic compounds, had a higher thickness-normalized water flux, and fouled less. The combination of the TFC QI membrane's selectivity with its reduced fouling propensity makes possible a treatment for hydraulic fracturing wastewater and other complex aqueous streams inaccessible by most commercial membranes, motivating the further study and development of the TFC QI membrane.

Current commercial nanofiltration and reverse osmosis membranes are limited in scope and performance due to their physicochemical properties. Desalination of hydraulic fracturing wastewater poses a particular challenge to membrane filtration given the high concentrations of both organic compounds and salts present in these waters. The recently-developed nanoporous, bicontinuous cubic, lyotropic liquid crystal, thin-film-composite polymer membrane (TFC QI membrane), having unique physicochemical properties, enables an alternative treatment of hydraulic fracturing wastewater. Specifically, the TFC QI membrane recovers the organic compounds from this high-salinity wastewater, enabling biodegradation to occur after desalination. However, other performance criteria must be demonstrated for a membrane to reach application. The work presented herein demonstrates the stable performance of the TFC QI membrane during 66 h of cross-flow filtration of hydraulic fracturing produced water. Compared to the commercial NF90 membrane, the TFC QI membrane recovered a larger portion of the organic compounds, had a higher thickness-normalized water flux, and fouled less. The combination of the TFC QI membrane's selectivity with its reduced fouling propensity makes possible a treatment for hydraulic fracturing wastewater and other complex aqueous streams inaccessible by most commercial membranes, motivating the further study and development of the TFC QI membrane.

With the advent of antibiotic resistant organisms, development of alternate classes of molecules other than antibiotics to combat microbial infections, have become extremely important. In this context, antimicrobial peptides have taken center stage of antimicrobial therapeutic research. In this work, we have reported two cationic antimicrobial octapeptides WRL and LWRF, with broad spectrum antimicrobial activities against several strains of ESKAPE pathogens. Both the peptides were membrane associative and induced microbial cell death through membranolysis, being selective towards microbial membranes over mammalian membranes. The AMPs were unstructured in water, adopting partial helical conformation in the presence of microbial membrane mimics. Electrostatic interaction formed the primary basis of peptide-membrane interactions. WRL was more potent, salt tolerant and faster acting of the two AMPs, owing to the presence of two tryptophan residues against that of one in LWRF. Increased tryptophan number in WRL enhanced its membrane association ability, resulting in higher antimicrobial potency but lower selectivity. This experimental and computational work, established that an optimum number of tryptophan residues and their position was critical for obtaining high antimicrobial potency and selectivity simultaneously in the designed cationic AMPs. Understanding the peptide membrane interactions in atomistic details can lead to development of better antimicrobial therapeutics in future., (© 2024 Wiley-VCH GmbH.)

Sodium alginate (SA) is a progressive material for membrane fabrication. The technological development of SA‐based membranes has made a significant contribution to the separation techniques, especially in aqueous organic solutions. The outstanding performance of SA is attributed to its outstanding structural flexibility and hydrophilicity. In view of structural characteristics, SA membranes have immense utilization in the pervaporation separation of organics. Among various organics, dehydration of aqueous ethanol is employed as a standard to check the success of pervaporation (PV) membrane. Because ethanol and water have comparable molecular sizes, thus difficult to extract water from aqueous ethanol mixtures than it is for other organics. A literature survey shows that wide‐ranging data are available on the PV performance of SA and its modified membranes. In this context, the present review addresses the recent advances made in SA membranes for enhanced ethanol dehydration performance during the last decade. Available data since 2010 has been compiled for grafted, crosslinked, blend, mixed matrix, and composite hybrid sodium alginate membranes in terms of separation factor, permeation flux, and pervaporation separation index PSI. The data are assessed with reference to the effect of feed composition, membrane selectivity, flux, and swelling behavior. [ABSTRACT FROM AUTHOR]

High‐precision separation with increased water permeability is critical for efficient membrane‐based water treatment processes. To achieve high selectivity toward different targeted species while allowing rapid water transportation, the structure of the membrane polyamide selective layer requires delicate regulation. Herein, an effective approach to systematically expand the pore size of polyamide layers by incorporating ammonium ion‐modified carbon dots (CDs) into the polyamide network is developed. The ammonium ions with different alkyl chain lengths attached to the CDs create nanochannels of different sizes in the network to lower the energy barrier for water transportation while maintaining high selectivity to targeted species. When the alkyl chain length of the ammonium ions reaches eight carbon atoms (i.e., C8 ions), the amphiphilic C8‐CDs induce the formation of the ridged nanostructure on the membrane surface and hence the increased membrane filtration area. The resultant thin‐film nanocomposite (TFN) membrane, denoted as the TFN‐C8‐CDs membrane, demonstrates a higher Na2SO4 rejection of 98.9% and NaCl/Na2SO4 selectivity of 83.1 than the pristine polyamide membrane, together with a tripled pure water permeability of 29.0 L m−2 h−1 bar−1. Herein, a viable approach for ingeniously designing the nanochannels and surface nanostructure of polyamide membranes for more efficient filtration processes is provided. [ABSTRACT FROM AUTHOR]

High‐precision separation with increased water permeability is critical for efficient membrane‐based water treatment processes. To achieve high selectivity toward different targeted species while allowing rapid water transportation, the structure of the membrane polyamide selective layer requires delicate regulation. Herein, an effective approach to systematically expand the pore size of polyamide layers by incorporating ammonium ion‐modified carbon dots (CDs) into the polyamide network is developed. The ammonium ions with different alkyl chain lengths attached to the CDs create nanochannels of different sizes in the network to lower the energy barrier for water transportation while maintaining high selectivity to targeted species. When the alkyl chain length of the ammonium ions reaches eight carbon atoms (i.e., C8 ions), the amphiphilic C8‐CDs induce the formation of the ridged nanostructure on the membrane surface and hence the increased membrane filtration area. The resultant thin‐film nanocomposite (TFN) membrane, denoted as the TFN‐C8‐CDs membrane, demonstrates a higher Na2SO4 rejection of 98.9% and NaCl/Na2SO4 selectivity of 83.1 than the pristine polyamide membrane, together with a tripled pure water permeability of 29.0 L m−2 h−1 bar−1. Herein, a viable approach for ingeniously designing the nanochannels and surface nanostructure of polyamide membranes for more efficient filtration processes is provided.

Graphene, in spite of exceptional physio-chemical properties, still faces great limitations in its use and industrial scale-up as highly selective membranes (enhanced ratio of proton conductivity to fuel cross-over) in liquid alcohol fuel cells (LAFCs), due to complexity and high cost of prevailing production methods. To resolve these issues, a facile, low-cost and eco-friendly approach of liquid phase exfoliation (bath sonication) of graphite to obtain graphene and spray depositing the prepared graphene flakes, above anode catalyst layer (near the membrane in the membrane electrode assembly (MEA)) as barrier layer at different weight percentages relative to the base membrane Nafion 115 was utilized in this work. The 5 wt.% nano-graphene layer raises 1 M methanol/oxygen fuel cell power density by 38% to 91 mW·cm−2, compared to standard membrane electrode assembly (MEA) performance of 63 mW·cm−2, owing to less methanol crossover with mild decrease in proton conductivity, showing negligible voltage decays over 20 h of operation at 50 mA·cm−2. Overall, this work opens three prominent favorable prospects: exploring the usage of nano-materials prepared by liquid phase exfoliation approach, their effective usage in ion-transport membrane region of MEA and enhancing fuel cell power performance. [ABSTRACT FROM AUTHOR]

The SPEEK-PVA-Silica hybrid membranes are prepared by solution casting method. The physical, chemical and electrical properties of the polymer membranes are studied by FESEM, FTIR, XRD, DSC, TGA, DMA, water and methanol uptake capacity, Ion Exchange Capacity (IEC), Degree of Sulfonation (DS), hydration number (λ), void volume fraction (%), methanol permeability and proton conductivity. The void volume fraction and density of the polymer membrane increases with increase in the silica content of the membrane which decreases glass transition temperature. At 30 °C, the maximum proton conductivity is found for SPS-3 membrane (3.8 × 10–2 S/cm) which is much higher than recast SPEEK membrane (2.9 × 10–2 S/cm). The proton conductivity of the polymer membrane is dominated by free water facilitated vehicular mechanism. The improvement of the conductivity of the proton in the silica filled polymer membrane at medium to higher temperature is due to the strong interaction between the silica and water resulting in a reduction in the loss of evaporation of water as well as an improvement in the bound water content of the polymer channel, which is regulated by the Grotthuss mechanism. The reduction of methanol permeability and increment in membrane selectivity clearly confirms that the silica filled polymer have excellent methanol blocking capacity which is beneficial for direct methanol fuel cell design. [ABSTRACT FROM AUTHOR]

The increasing demand for nanofiltration processes in drinking water treatment, industrial separation and wastewater treatment processes has highlighted several shortcomings of current state-of-the-art thin film composite (TFC NF) membranes, including limitations in chemical resistance, fouling resistance and selectivity. Polyelectrolyte multilayer (PEM) membranes provide a viable, industrially applicable alternative, providing significant improvements in these limitations. Laboratory experiments using artificial feedwaters have demonstrated selectivity an order of magnitude higher than polyamide NF, significantly higher fouling resistance and excellent chemical resistance (e.g., 200,000 ppmh chlorine resistance and stability over the 0–14 pH range). This review provides a brief overview of the various parameters that can be modified during the layer-by-layer procedure to determine and fine-tune the properties of the resulting NF membrane. The different parameters that can be adjusted during the layer-by-layer process are presented, which are used to optimize the properties of the resulting nanofiltration membrane. Substantial progress in PEM membrane development is presented, particularly selectivity improvements, of which the most promising route seems to be asymmetric PEM NF membranes, offering a breakthrough in active layer thickness and organic/salt selectivity: an average of 98% micropollutant rejection coupled with a NaCl rejection below 15%. Advantages for wastewater treatment are highlighted, including high selectivity, fouling resistance, chemical stability and a wide range of cleaning methods. Additionally, disadvantages of the current PEM NF membranes are also outlined; while these may impede their use in some industrial wastewater applications, they are largely not restrictive. The effect of realistic feeds (wastewaters and challenging surface waters) on PEM NF membrane performance is also presented: pilot studies conducted for up to 12 months show stable rejection values and no significant irreversible fouling. We close our review by identifying research areas where further studies are needed to facilitate the adoption of this notable technology.

Peptide design and drug development offer a promising solution for combating serious diseases or infections. In this study, using an AI-human negotiation approach, we have designed a class of minimal model peptides against tuberculosis (TB), among which K7W6 exhibits potent efficacy attributed to its assembly-induced function. Comprising lysine and tryptophan with an amphiphilic α-helical structure, the K7W6 sequence exhibits robust activity against various infectious bacteria causing TB (including clinically isolated and drug-resistant strains) both in vitro and in vivo . Moreover, it synergistically enhances the effectiveness of the first-line antibiotic rifampicin while displaying low potential for inducing drug resistance and minimal toxicity toward mammalian cells. Biophysical experiments and simulations elucidate that K7W6's exceptional performance can be ascribed to its highly selective and efficient membrane permeabilization activity induced by its distinctive self-assembly behavior. Additionally, these assemblies regulate the interplay between enthalpy and entropy during K7W6-membrane interaction, leading to the peptide's two-step mechanism of membrane interaction. These findings provide valuable insights into rational design principles for developing advanced peptide-based drugs while uncovering the functional role played by assembly.

Membrane scaling problems can limit broad applications of electrodialysis (ED) for nutrients recovery from wastewater. In this study, we investigated the calcium- and magnesium-scale precipitation on ion-exchange membranes (IEMs) using a laboratory-scale ED reactor. Two high-strength wastewater streams, including municipal waste (MW) liquid digestate and food waste (FW) liquid digestate, were fed into the ED reactor. For the operation with MW liquid digestate, the cumulative Ca2+ loss increased with the increasing electric current, while the electric current conditions did not affect the cumulative Mg2+ loss. After 8-h operation, 60.1% of Ca2+ and 39.0% of Mg2+ in the MW liquid digestate were lost in the form of precipitates. Observed scalants on cation-exchange membranes were vaterite, amorphous calcium carbonate (ACC), and struvite, while ACC was not found on anion-exchange membranes. Observed scalants of calcium carbonate with MW liquid digestate (vaterite and ACC) were different from scalants (calcite) found with synthetic solutions. Among these scalants, struvite was formed as sharp (needle-shaped) crystals that can potentially damage the IEM. The gradual loss of Mg2+ was observed with FW liquid digestate because of high PO43− concentration, indicating the formation of struvite. The membrane with high selectivity for divalent ions resulted in the rapid decrease in electric current, implying serious membrane scaling on IEMs. These findings demonstrated that the membrane scaling problems by calcium and magnesium precipitation are ubiquitous in ED for nutrients recovery from wastewater. [ABSTRACT FROM AUTHOR]

Lignin is a promising raw material for membrane fabrication due to its abundant oxygen-containing functional groups, branched molecular structure, and high abundance in the botanic field. In this report, polydopamine (PDA) coated carbon nanotubes (PCNTs) are synthesized. Then, a PCNT-incorporated lignin-based loose nanofiltration membrane is fabricated using quaternized lignin (QL) as a raw material, triphosgene (TP) as a crosslinker, and PCNTs as nanoadditive by interfacial polymerization. The results show that the PCNTs uniformly distribute in the QL-based separation layer providing quick diffusion paths for water molecules and salt ions. The coated PDA layer improves the chemical compatibility between the PCNTs and the separation layer. The incorporated PCNTs optimize the membrane microstructure and elevate the pure water permeance to 45.5 LMH bar−1. The membrane exhibits high rejections to various dyes (> 90%) and high salt permeation (> 90%), demonstrating an excellent dye/salt separation performance. Moreover, it has satisfactory capabilities for resisting dye adsorption and fouling, and its separation capability also has good tolerances to the acid, alkali, and active chlorine treatments. The quaternary ammonium ions and hydrophilic surface endow the membrane with favorable bactericidal property (99.3%) and bacteria-adhesion resistance. Besides, TP is a better crosslinker than trimesoyl chloride for optimizing the membrane microstructure and crosslinking degree in terms of dye/salt separation. [Display omitted] • A novel LNF membrane is obtained by using TP to crosslink quaternized lignin. • The membrane exhibits high permeance, dye rejection, and salt permeation. • Introducing PDA-coated CNTs can improve permeance and selectivity of the membrane. • The membrane has resistance to acid, alkali, active chlorine, and dye fouling. • Quaternary ammonium groups improve the antibacterial property of the membrane. [ABSTRACT FROM AUTHOR]

Yuzhang Liu,1,2,* Qiang Du,1,* Chengbang Ma,2 Xinping Xi,2 Lei Wang,2 Mei Zhou,2 James F Burrows,2 Tianbao Chen,2 Hui Wang1 1School of Pharmacy, China Medical University, Shenyang 110001, Liaoning, China; 2Faculty of Medicine, Health and Life Sciences, School of Pharmacy, Queen’s University Belfast, Belfast BT9 7BL, Northern Ireland, UK *These authors contributed equally to this work Background: Antimicrobial peptides (AMPs) from the skin secretions of amphibians are now considered as a potential alternative to conventional antibiotics. Phylloseptins are a family of AMPs identified in the skin secretions of Phyllomedusinae tree frogs which exhibit highly conserved structural characteristics. This study examines the structure–activity relationship of the newly discovered phylloseptin, Phylloseptin-PHa (PSPHa) from Pithecopus hypochondrialis. Materials and methods: PSPHa and modified analogs were produced by solid phase synthesis and purified by reverse-phase HPLC. Rationally designed modified analogs incorporating changes in significant physicochemical parameters such as hydrophobicity, hydrophobic moment and net charge were investigated to determine their influence on secondary structure, antimicrobial activity, membrane permeabilization and cytotoxicity. Results: Overall, we found that when rationally designing AMPs by altering their primary structure it is important to keep a balance between hydrophobicity and charge. Conclusion: This study provides new insights which will help in the future development of AMPs as alternatives to conventional antibiotics for the treatment of Staphylococcus aureus and methicillin-resistant S. aureus infections. Keywords: phylloseptin, antimicrobial activity, hydrophobicity, charge, membrane selectivity

Graphene, in spite of exceptional physio-chemical properties, still faces great limitations in its use and industrial scale-up as highly selective membranes (enhanced ratio of proton conductivity to fuel cross-over) in liquid alcohol fuel cells (LAFCs), due to complexity and high cost of prevailing production methods. To resolve these issues, a facile, low-cost and eco-friendly approach of liquid phase exfoliation (bath sonication) of graphite to obtain graphene and spray depositing the prepared graphene flakes, above anode catalyst layer (near the membrane in the membrane electrode assembly (MEA)) as barrier layer at different weight percentages relative to the base membrane Nafion 115 was utilized in this work. The 5 wt.% nano-graphene layer raises 1 M methanol/oxygen fuel cell power density by 38% to 91 mW·cm−2, compared to standard membrane electrode assembly (MEA) performance of 63 mW·cm−2, owing to less methanol crossover with mild decrease in proton conductivity, showing negligible voltage decays over 20 h of operation at 50 mA·cm−2. Overall, this work opens three prominent favorable prospects: exploring the usage of nano-materials prepared by liquid phase exfoliation approach, their effective usage in ion-transport membrane region of MEA and enhancing fuel cell power performance.

Electrodialysis is a water desalination technology that enables selective separation of ions, making it a promising solution for sustainable water reuse. The selectivity of the process is mainly determined by the properties of ion exchange membranes that can vary depending on the composition of ions in water, such as water uptake and charge density. In this work, we studied selective adsorption of Na + and K + ions in various ion exchange membranes considering the effect of solution ion composition on membrane water volume fraction. For that purpose, we conducted membrane adsorption experiments using solutions with Na + and K + ions with different ion compositions including Li + , Ca 2+ or Mg 2+ ions at different concentrations (0.001 - 0.25 M). The experiments showed that with the total ion concentration and the amount of divalent ions in solution, the membrane water volume fraction decreases while the selective adsorption of the smaller (hydrated) K + ions over the Na + ions in the membrane increases. We developed a theoretical framework based on Boublik-Mansoori-Carnahan-Starling-Leland (BMCSL) theory to describe the effect of membrane water volume fraction on selective adsorption of the ions by including volumetric effects, such as size exclusion. The developed framework was used to describe ion partitioning results of the membrane adsorption experiments. In addition, the effect of solution ion composition on selective ion removal during electrodialysis operation was evaluated using experimental data and theoretical calculations. The results of this study show that considering volumetric effects can improve the ion partitioning description in ion exchange membranes for solutions with various ion compositions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

The recent expansion of global Lithium Ion Battery (LIBs) production has generated a significant stress on the lithium demand. One of the means to produce this element is its extraction from different aqueous sources (salars, geothermal water etc.). However, the presence of other mono- and divalent cations makes this extraction relatively complex. Herein, we propose lithium-sodium separation by an electrodialysis (ED) process using a Lithium Composite Membrane (LCM), whose effectiveness was previously demonstrated by a Diffusion Dialysis process (previous work). LCM performances in terms of lithium Recovery Ratio (RR(Li+)) and Selectivity (S(Li/Na)) were investigated using different Li+/Na+ reconstituted solutions and two ED cells: a two-compartment cell was chosen for its simplicity, and a four-compartment one was selected for its potential to isolate the redox reactions at the electrodes. We demonstrated that the four-compartment cell use was advantageous since it provided membrane protection from protons and gases generated by the electrodes but that membrane selectivity was negatively affected. The impact of the applied current density and the concentration ratio of Na+ and Li+ in the feed compartment ([Na+]F/[Li+]F) were tested using the four-compartment cell. We showed that increasing the current density led to an improvement of RR(Li+) but to a reduction in the LCM selectivity towards Li+. Increasing the [Na+]F/[Li+]F ratios to 10 had a positive effect on the membrane performance. However, for high values of this ratio, both RR(Li+) and S(Li/Na) decreased. The optimal results were obtained at [Na+]F/[Li+]F near 10, where we succeeded in extracting more than 10% of the initial Li+ concentration with a selectivity value around 112 after 4 h of ED experiment at 0.5 mA·cm−2. Thus, we can objectively estimate that the concept of this selective extraction of Li+ from a mixture even when concentrated in Na+ using an ED process was validated.

The efficiency of enzymatic depolymerization in a membrane reactor was investigated. The model analysis was performed on bovine serum albumin hydrolysis reaction led by three different enzymes, for which kinetic equations have different forms. Comparing to a classic reactor, the reaction yield turns out to be distinctly higher for all types of kinetics. The effect arises from increasing (thanks to the proper selectivity of the applied membrane) the concentration of reagents in the reaction volume. The investigations indicated the importance of membrane selectivity election, residence time and at non-competitive inhibition the substrate (biopolymer) concentration in feed stream. Presented analysis is helpful in these parameters choice for enzymatic hydrolysis of different biopolymers.

At this point in history, mankind faces a daunting challenge: how are we to produce high-grade foods without damage to the environment? The only possible rational solution lies in the efficient use of natural raw materials. However, the practical side of the matter cannot be resolved without innovative food equipment designed on the basis of the latest scientific achievements. The current research features the theory and practice of curd whey and skimmed milk ultrafiltration. It focuses on the main operating parameters of the equipment involved and the maximum permissible value of the milk solids content. The experiment included whey, obtained as a byproduct of cottage cheese processing, and skimmed milk, obtained by whole milk separation. The membrane method in the processing of secondary dairy raw materials allows for an environmentally-friendly waste-free production. It is a promising trend in the modern food industry: it creates opportunities for a large range of novel dairy products, beverages, and animal feed, as well as for other sustainable technologies. The paper describes how the volume of permeate flux mass transfer and the selectivity of polysulfonamide ultrafiltration membranes (PSA-20 and PSA-50) depend on the volume of operating load and circulation rate during whey and skimmed milk separation. The authors analyzed the mass transfer and the hydrodynamics in the channel of a roll type baromembrane, including the gel formation process. They established the influence of the milk solids weight ratio in the liquid polydisperse system on the permeate flux volume and the selectivity of the polysulfonamide ultrafiltration membrane (PSA-50).

This study describes the use of regenerated cellulose (RCA) membranes with molecular weight cut-off (MWCO) values of 10, 30, and 100 kDa, respectively, to separate phytosterols from orange juice for possible nutraceutical production. A desirable membrane separation rejects protein whilst transmitting phytosterols and other low molecular mass compounds such as sugars. The ultrafiltration was performed in a cross-flow membrane system with a total filtration area of 336 cm2. Total phytosterol analysis was carried out by using a Liebermann-Buchard-based method. Protein concentration was quantified by the Bradford method. The effects of three different membranes upon the rejection of total phytosterol content, proteins, sugar, and antioxidant activity were studied. Of the membranes tested, the 10-kDa membrane displayed the highest concentration of phytosterols in the permeate. The 30-kDa and 100-kDa membranes gave comparatively higher phytosterol rejection. The membrane surface roughness and corresponding pure water flux values varied as a function of MWCO such that RCA30 > RCA100 > RCA10. Membranes with rougher surfaces displayed higher fouling than those with smoother surfaces. Hydrophobicity and surface roughness both influenced filtration performance, by controlling the development of the protein-based foulant which modified membrane selectivity. [ABSTRACT FROM AUTHOR]

Sulfonated polyethersulfone (SPES), polyaniline (PANI), and Cloisite 15 A® were used as modifiers for the fabrication of Mindel composite polymer electrolyte membranes (PEMs). Pristine Mindel and Mindel composite PEMs were fabricated by the solution intercalation technique. The presence of modifiers in the Mindel membrane matrix was confirmed by Fourier transform infrared (FTIR) studies. The primary characteristics of pristine Mindel and Mindel PEMs such as water uptake, methanol uptake, proton conductivity ion‐exchange capacity (IEC), and chemical and mechanical stability were evaluated. The pore size of Mindel/SPES/Cloisite 15 composite PEM was increased owing to the addition of SPES and Cloisite 15. The higher proton conductivity of 4.323 × 10−4 S cm−1, enhanced IEC of 0.482 mequiv. g−1, and maximum water uptake (%) of 38.12 were noted for Mindel/SPES/Cloisite membrane. Membrane selectivity of all Mindel PEMs was enhanced by the addition of modifiers. The results of this study indicate that Mindel composite membranes could be utilized as PEMs for direct methanol fuel cell (DMFC). [ABSTRACT FROM AUTHOR]

Ion exchange membranes allowing the passage of charge-carrying ions have established their critical role in water, environmental, and energy-relevant applications. The design strategies for high-performance ion exchange membranes have evolved beyond creating microphase-separated membrane morphologies, which include advanced ion exchange membranes to ion-selective membranes. The properties and functions of ion-selective membranes have been repeatedly updated by the emergence of materials with subnanometer-sized pores and the understanding of ion movement under confined micropore ion channels. These research progresses have motivated researchers to consider even greater aims in the field, i.e., replicating the functions of ion channels in living cells with exotic materials or at least targeting fast and ion-specific transmembrane conduction. To help realize such goals, we briefly outline and comment on the fundamentals of rationally designing membrane pore channels for ultrafast and specific ion conduction, pore architecture/chemistry, and membrane materials. Challenges are discussed, and perspectives and outlooks are given.

Treatment of Staphylococcus aureus infections is complicated by the development of antibiotic tolerance, a consequence of the ability of S. aureus to enter into a nongrowing, dormant state in which the organisms are referred to as persisters. We report that the clinically approved anthelmintic agent bithionol kills methicillinresistant S. aureus (MRSA) persister cells, which correlates with its ability to disrupt the integrity of Gram-positive bacterial membranes. Critically, bithionol exhibits significant selectivity for bacterial compared with mammalian cell membranes. All-atom molecular dynamics (MD) simulations demonstrate that the selectivity of bithionol for bacterial membranes correlates with its ability to penetrate and embed in bacterial-mimic lipid bilayers, but not in cholesterol-rich mammalian-mimic lipid bilayers. In addition to causing rapid membrane permeabilization, the insertion of bithionol increases membrane fluidity. By using bithionol and nTZDpa (another membraneactive antimicrobial agent), as well as analogs of these compounds, we show that the activity of membrane-active compounds against MRSA persisters positively correlates with their ability to increase membrane fluidity, thereby establishing an accurate biophysical indicator for estimating antipersister potency. Finally, we demonstrate that, in combination with gentamicin, bithionol effectively reduces bacterial burdens in a mouse model of chronic deep-seated MRSA infection. This work highlights the potential repurposing of bithionol as an antipersister therapeutic agent. [ABSTRACT FROM AUTHOR]

The objective of this study was to enable precise evaluation of Donnan separations, under diffusion controlled conditions, using the ion exchange membrane selectivity coefficient, Kc. This was accomplished by experimental measurement of the selectivity of Selemion® AMV anion-exchange membrane toward nitrate, bicarbonate, phosphate and sulfate, and analyzing batch Donnan separations data of these target ions with NaCl stripping solution according to flux equations which take into account the membrane selectivity. By fitting the experimental separation data to the model equations, kinetic coefficients characterizing the Donnan dialysis were determined for both the simplified case of Kc = 1 and for the more precise case based on the experimental Kc value. The difference in the kinetic coefficient based on the simplified case of Kc = 1 and on the experimental Kc value is around 10% for sulfate ions, 20% for the nitrate and bicarbonate ions and approximately 40% for the phosphate. These differences may cause deviation in evaluating the time required to achieve a desired target ion removal. [ABSTRACT FROM AUTHOR]

Electrospun nanofiber hybrid membranes have superior membrane performance due to their high specific surface area, narrow pore size, high porosity, and uniform pore size. Recently, increasing attention has been given to hydrophilic membranes such as polyamide 6 (PA6) in applications microfiltration and reverse osmosis. Electrospun PA6 nanofiber hybrid membranes have not found any real application due to their poor mechanical strength under high pressure. In this study, PA6 nanofiber layer was prepared using wire electrospinning method. Three supporting material with different adhesion method has been used to improve the mechanical properties of the membranes. Membranes were characterized with Scanning Electron Microscope images, pore size, and contact angle measurements. Tensile strength and the delamination tests were run to measure the mechanical properties of the membranes. Three types of wastewater were carried out during filtration; using real wastewater supplied from a company which consists of pitch and tar oils, engine oil/water mixture and kitchen oil/water mixture. Results indicated that the adhesion method and the supporting layer played a big role in the permeability of the membranes. The PA6 nanofiber hybrid membranes exhibited high water fluxes in even at low pressures which indicate that electrospun nanofiber membranes might be highly promising for microfiltration applications. [ABSTRACT FROM AUTHOR]

Sulfonic acid-functionalized polymer electrolyte membranes alternative to Nafion® were developed. These were hydrocarbon systems, such as blend sulfonated polyetheretherketone (s-PEEK), new generation perfluorosulfonic acid (PFSA) systems, and composite zirconium phosphate–PFSA polymers. The membranes varied in terms of composition, equivalent weight, thickness, and filler and were investigated with regard to their methanol permeation characteristics and proton conductivity for application in direct methanol fuel cells. The behavior of the membrane electrode assemblies (MEA) was investigated in fuel cell with the aim to individuate a correlation between membrane characteristics and their performance in a direct methanol fuel cell (DMFC). The power density of the DMFC at 60 °C increased according to a square root-like function of the membrane selectivity. This was defined as the reciprocal of the product between area specific resistance and crossover. The power density achieved at 60 °C for the most promising s-PEEK-based membrane-electrode assembly (MEA) was higher than the benchmark Nafion® 115-based MEA (77 mW·cm−2 vs. 64 mW·cm−2). This result was due to a lower methanol crossover (47 mA·cm−2 equivalent current density for s-PEEK vs. 120 mA·cm−2 for Nafion® 115 at 60 °C as recorded at OCV with 2 M methanol) and a suitable area specific resistance (0.15 Ohm cm2 for s-PEEK vs. 0.22 Ohm cm2 for Nafion® 115).

The task of this work was to construct the mixed matrix membrane based on polymer that could be used for the treatment of the waste gases. Therefore, high permeability for the carbon dioxide and low permeability for other gases commonly present in the industrial combustion waste gases (nitrogen, oxygen, hydrogen, methane) are essential. Those membranes belong to the group of dense composite membranes, and mechanism for separation is based on the solution-diffusion mechanism. In this paper, feasibility of the application of poly(ethyleneoxid)-copoly(phtalamide) was tested. In order to enchase the permeability of carbon dioxide, three different zeolites were incorporated, and in order to improve compatibility between the inorganic particles and polymer chains, n-tetradecyldimethylamonium bromide (NTAB).was added. Three zeolites were with the 2-dimensional pores (IHW, NSI and TER). The best results in carbon dioxide/hydrogen selectivity were obtained with the membrane constructed with PEBAX 1657 and surface treated zeolites, while the better results concerning selectivity were gained with membranes based on the Polyactive. [Projekat Ministarstva nauke Republike Srbnije, br. TR 34011 i br. III 45019]

The main task of the work is to construct the polymeric membrane that could be used for the waste gases treatment. For this purpose, membrane must have high permeability for the carbon dioxide and low permeability of the other gases commonly present in waste gases (hydrogen, oxygen, nitrogen and methane). The constructed membranes were of a dense type, based on a solubility/diffusivity mechanism. In order to enchase the permeability of carbon dioxide, four different zeolytes were added, and in order to improve mechanical stability two different additives were tested. Three zeolytes were with the 3-dimensional pores (ZSM5; Faujasite Linde type A) and one was with the 1-dimensional pores (Linde type L). As an additive, n-tetradecyldimethylamonium bromide - n-C14TMABr was tested. The aim of an additive was to provide good wetting of a highly electrically charged zeolyte particle by the hydrophobic polymer chains. The other examined additive was dimethylaminopyridine (DMAP) which should improve the solubility of carbon dioxide due to its alkali properties. The best results in carbon dioxide/hydrogen selectivity and permeability were obtained with the membrane constructed with PEBAX 1657 and surface treated zeolyte. The obtained permeability of carbon dioxide was 128 Barrer, and the carbon dioxide/hydrogen selectivity was 9.7.

Gas translation diffusion is proposed to compete with surface diffusion for describing the permeation of light gases (He, H 2 , CO 2 and CO) through zeolite membranes. The analysis for both DD3R and NaY zeolite membranes shows some differences in H 2 , CO and CO 2 permeation for both binary/ternary gas mixture and single gas. The permeation description through gas translation of weakly adsorbed species such as, e.g., H 2 , specifically at low temperatures, is more accurate than that obtained by Knudsen diffusion in a previous work. Gas translation paired to surface diffusion well reproduces the maximum in H 2 flux, which was missed by the Knudsen diffusion (Caravella et al., 2016) [13]. The strongly adsorbed species are less dependent on gas translation or Knudsen diffusion since the surface diffusion is very significant in the whole temperature range investigated. The gas translation was demonstrated to reproduce the permeation through zeolite membranes better than Knudsen diffusion. This paper attempts to discriminate the operating mechanisms among gas translation, surface and Knudsen diffusion in gas mixture permeation through zeolite membranes. [ABSTRACT FROM AUTHOR]

In recent years, molecular-sieve graphene oxide (GO) membranes have shown a great potential to realize high-flux and high-selectivity mixture separation, at low energy cost. Hence, in this study, GO nanocomposite membranes were prepared for hydrogen separation. To this purpose, the modified tubular γ-alumina supports were prepared by coating boehmite sol on α-alumina support. Then, the GO top layer was coated on the modified γ-alumina support using GO colloidal sol prepared by modified hummer method. Consequently, effects of various concentrations of dip-coating sol were evaluated on GO graphene membrane performance, in terms of hydrogen separation at various pressure gradient and temperatures. Regarding to characterization analyses, uniform GO layer formation was confirmed on modified support. As a result of gas permeance test of GO nanocomposite membrane, pressure gradient effect was positive on membrane performance, while negative effect on H 2 /CO 2 and H 2 /N 2 selectivities was indicated versus lowest concentration of dip coating sol. On the other, for all cases, negative effect was observed for hydrogen selectivity versus temperature. In particular, for the best GO membrane sample, at room temperature and 3 bar pressure gradient, H 2 /CO 2 and H 2 /N 2 values were obtained 38.5 and 16.5 (H 2 permeance equal 5.9 ∗ 10 −7  mol/m 2  s Pa), respectively, while these parameters values at 473 K and 1 bar pressure gradient were 15.7, 10.6 (H 2 permeance equal 7.6 ∗ 10 −7  mol/m 2  s Pa). Moreover, regarding to effects of dip-coating sol concentration, the best choice was introduced sample 1 (with highest concentration of dip coating sol) from performance viewpoint. [ABSTRACT FROM AUTHOR]

A fully dynamic model for mixture gas separation is built in Cu-BTC membranes. A multi-scale method that couples the lattice Boltzmann method with grand canonical Monte Carlo (GCMC) is proposed to investigate the mass transfer process of CO 2 /CH 4 mixture gases in Cu-BTC membranes. The convection and diffusion in the interparticle flow field and the intraparticle diffusion and adsorption in the particle interior are simultaneously considered. The membrane morphology is reconstructed by a sphere-based simulated annealing method. The effects of membrane porosity and particle size on the mass transfer and selectivity of CO 2 /CH 4 mixture gases are predicted. Results show that the selectivity of CO 2 /CH 4 is mainly determined by interparticle and intraparticle mass transfer resistances. Meanwhile, the time of saturation adsorption for CO 2 and CH 4 both decrease with an increase in porosity but decreases for CO 2 and increases for CH 4 with an increase in particle size. The selectivity of CO 2 /CH 4 in Cu-BTC membranes decreases with an increase in porosity and particle size. Therefore, membranes with small porosity and particle size should be utilized. Compared with the traditional binary GCMC and ISAT methods based on saturation adsorption, the proposed coupled method is closer to the physical essence of the process because it considers dynamic competitive adsorption. The present method can be helpful in the design of efficient metal–organic framework (MOF) membranes. [ABSTRACT FROM AUTHOR]

• Multi-ionic solutions in Electrodialysis with bipolar membrane (EDBM) were studied. • A new methodology for evaluating the ion transport in EDBM systems was proposed. • Apparent ion transport numbers and selectivities were calculated and discussed. • Enhanced chloride transport across AEMs and potassium across the CEMs were found. • Results showed SEC of 1.6 kWh kg−1 and current efficiency of 75% with real brines. Electrodialysis with Bipolar Membranes (EDBM) has become a key technology for valorising waste brine streams as a new chemical production route. Even though its application has been widely studied using single electrolyte solutions (e.g., NaCl or Na 2 SO 4), there is still a lack of knowledge about using multi-ionic mixtures. For the first time, this work aims to evaluate the EDBM performance when treating synthetic solutions mimicking the waste brines produced in a integrated process for the valorisation of solar saltworks bitterns. The behaviour of a lab-scale EDBM unit was assessed using SUEZ ion exchange membranes (IEMs), operating at 300 A m−2, and the ion transport through IEMs was investigated, based on the calculation of apparent transport numbers and selectivities. The results highlighted that multi-ionic solutions barely affected the production of hydroxide ions. Chlorides were transported up to 7 times faster than sulphates across the anion-exchange membranes, while the cation-exchange membranes exhibited slightly higher selectivity for potassium than for sodium (∼1.2). The current efficiencies ranged between 70 % and 80 %, while a minimum specific energy consumption of 1.60 kWh kg-1 NaOH was obtained for the most concentrated brine at 1 mol L-1 OH–. These results provide novel and valuable information to support the development and implementation of EDBM as a sustainable technology for supporting a resource-efficient and competitive economy through on-site and delocalized chemicals production routes. [ABSTRACT FROM AUTHOR]

Membrane fouling is one of the main issues in membrane processes, leading to a progressive decrease of permeability. High fouling rates strongly reduce the productivity of the membrane plant, and negatively affect the surviving rate of the membrane modules, especially when real wastewater is treated. On the other hand, since selectivity must meet certain target requirements, fouling may lead to unexpected selectivity improvements due to the formation of an additional superficial layer formed of foulants and that act like a selective secondary membrane layer. In this case, a certain amount of fouling may be profitable to the point where selectivity targets were reached and productivity is not significantly affected. In this work, the secondary clarifier of a step sludge recirculation bioreactor treating municipal wastewater was replaced by a membrane unit, aiming at recovering return sludge and producing purified water. Fouling issues of such a system were checked by boundary flux measurements. A simple model for the description of the observed productivity and selectivity values as a function of membrane fouling is proposed.

A thin-film composite, bicontinuous cubic lyotropic liquid crystal polymer (TFC Q I ) membrane with uniform-size, ionic nanopores was studied for the treatment of hydraulic fracturing flowback water. The TFC Q I membrane performance was compared to those of a commercial nanofiltration (NF) membrane (NF270) and a commercial reverse osmosis (RO) membrane (SW30HR) for the filtration of flowback water from the Denver-Julesburg Basin. The permeability, salt rejection, and organic solute rejection for each membrane was evaluated. The results illustrate that the TFC Q I membrane maintained its performance to a similar degree as the commercial NF and RO membranes while demonstrating a unique selectivity not observed in the commercial membranes. Specifically, the TFC Q I membrane rejected 75% of the salt while recovering 9.6% of the dissolved organic carbon (DOC) and 50% of the water. Of particular interest was the recovery of labile DOC, which was assessed through biodegradation experiments. Analysis following biodegradation of the TFC Q I membrane permeate demonstrates the membrane's ability to recover labile DOC in a reduced-saline permeate. Improved recovery of labile DOC (increased to 22%) was demonstrated by reducing the pH of the flowback water. Therefore, the selectivity of the TFC Q I membrane provides an opportunity to recover resources from hydraulic fracturing flowback. [ABSTRACT FROM AUTHOR]

SSL-25 (SSLLEKGLDGAKKAVGGLGKLGKDA) is one of the shortest peptides present in human sweat and is produced after the proteolytic processing of the parent peptide dermcidin. Both peptides are reported to have antimicrobial function. To determine the structure of SSL-25 in lipid bilayers, a series of 19 F-labeled SSL-25 analogs were synthesized. Circular dichroism (CD) analysis showed that SSL-25 and all of its analogs formed α-helices in the presence of lipid vesicles, thus allowing a detailed analysis via oriented CD and solid-state NMR. The results suggest that SSL-25 resides on the membrane surface with a slight helix tilt angle. A detailed 19 F NMR analysis revealed that SSL-25 does not form a continuous helix. The α-helical structure of the N-terminal part of the peptide was preserved in membranes of different lipid compositions and at various peptide-to-lipid molar ratios, but the C-terminus was disordered and did not fold into a well-defined α-helical conformation. Furthermore, the NMR results showed that SSL-25 resides on the membrane surface and does not re-orient into the membrane in response to changes in either peptide concentration or membrane composition. SSL-25 does not aggregate and remains fully mobile within the membrane bilayer, as shown by 19 F NMR. SSL-25 has a high binding affinity toward bilayers mimicking bacterial lipid compositions, but does not bind to mammalian model membranes containing cholesterol. These observations may explain the selectivity of this peptide for bacterial membranes, and they are also in line with basic biophysical considerations on spontaneous lipid curvature and the general effect of cholesterol on peptide/lipid interactions. [ABSTRACT FROM AUTHOR]

Knudsen and surface contributions to permeation are evaluated for CO 2 , H 2 CH 4 , CO and N 2 in single gas and multicomponent mixtures through silicalite membranes. Specifically, a recently developed model [Caravella et al.., Micropor. mesopor. Mater. 235 (2016) 87–99] is used to quantify both contributions and the blocking effect on Knudsen diffusion owing to the adsorption inside the zeolite pores. This model is validated for silicalite using various experimental data from the open literature measured for several gas mixtures and in a wide range of temperature and pressure. The influence of the strongly adsorbed species on the permeation of the weakly adsorbed ones is analysed and discussed. Different feed mixtures are investigated, allowing the optimal operating conditions that guarantee good separation performance to be identified. It is found that the blocking effect causes a higher selectivity at lower temperatures, at which adsorption is relatively stronger. The model well reproduces and well predicts the behaviour of permeating mixtures as function of temperature, pressure and feed composition. [ABSTRACT FROM AUTHOR]

Living particles such as bacteria are able to transfer through membrane pores that are smaller than cell size due to the specific stiffness of this type of microorganism. This phenomenon can lead to a significant loss of selectivity in the filtration process, which is a major cause of concern in the sterilizing filtration step. This study investigates the retention of three bacteria strains: Escherichia coli CIP 54124, Pseudomonas aeruginosa CIP 103467 and Staphylococcus aureus CIP 53154 by model porous membranes for various operating conditions (transmembrane pressure, feed concentration and the physicochemical composition of filtered media with antibacterial agent added at sublethal concentration). The first part of this study is dedicated to defining the size and the nanomechanical properties of the envelope of the studied bacteria by microscopic techniques (Transmission electron microscopy & Atomic-force microscopy), in order to then explore the role of these quantifiable characteristics on the cell transfer through the pores by deformation mechanisms. Our results lead to the development of a numerical model to connect the observed retention efficiency of the filtration experiment and the microscopic information about individual particles. [ABSTRACT FROM AUTHOR]

A mathematical model of multicomponent ion transport through a cation-exchange membrane is developed based on the Nernst-Planck equation. A correlation for the non-linear potential gradient is derived from current density relation with fluxes. The boundary conditions are determined with the Donnan equilibrium at the membrane-solution interface, taking into account the convective flow. Effective diffusivities are used in the model based on the correlation of tortuosity and ionic diffusivities in free water. The model predicts the effect of an increase in current density on the ion concentrations inside the membrane. The model is fitted to the previously published experimental data. The effect of current density on the observed increase in voltage drop and the decrease in permselectivity has been analyzed using the available qualitative membrane swelling theories. The observed non-linear behavior of the membrane voltage drop versus current density can be explained by an increase in membrane pore diameter and an increase in the number of active pores. We show how the membrane pore diameter increases and dead-end pores open up when the current density is increased. Graphical Abstract: [ABSTRACT FROM AUTHOR]

New hydrolyzed ethylene vinyl acetate (EVA) (EVA-OH) membranes were synthesized via the EVA partial hydrolysis reaction for the use in the water/gas separation field. The reaction conditions of the partial hydrolysis were optimized in terms of the EVA-OH chemical structure by using 1D and 2D NMR spectroscopy. It has been shown that a change of the EVA-OH chemical composition (i.e. the ratio between vinyl alcohol (VOH) and vinyl acetate (VAc) repeating units) has a significant influence on the membrane crystallinity due to a different nature of the VOH and VAc repeating units. The VAc groups act as a "soft" (i.e. amorphous) segmental unit owing to the low organization of the polymer chains, whereas the VOH groups operate as a "rigid" (i.e. semi-crystalline) unit because of the formation of the VOH crystals via the interchain interactions (i.e. hydrogen bonding between free alcohol groups). Thus, the noticeable change of the EVA-OH glass transition temperature T g is observed depending on the hydrolysis degree – the T g value of the EVA-OH 1 membrane (i.e. with 44 wt% of VAc) is ⁓ −9 °C, while for the EVA-OH 5 membrane (i.e. with 9 wt% of VAc) it equals to ⁓ 19 °C. Such a change of the membrane morphology allowed us to optimize the mechanical and transport properties of EVA-OH membranes. The presence of the "rigid" VOH repeating units positively influences the membrane tensile stiffness and resistance, thereby preventing the membrane adhesive properties. Consequently, the EVA-OH membrane tensile stiffness, stress at break, and elongation are varied in the range of 2.5–204 MPa, 4–45 MPa, and 1450-600%, respectively, depending on the VOH content. Besides, the amorphous VAc segmental units generate a higher permeation flux (i.e. higher water/gas permeability), whereas the semi-crystalline VOH repeating units ensure the membrane barrier properties and improve its selectivity. In addition, EVA-OH polymer membranes demonstrate a promising CO 2 separation performance in terms of the gas selectivity. The best EVA-OH membrane shows the selectivity coefficient α(CO 2 /N 2) of ⁓ 75 and α(CO 2 /O 2) of ⁓ 13. [Display omitted] • New hydrolyzed ethylene vinyl acetate membranes were synthesized. • Chemical structure confirmed by FTIR and 1D and 2D NMR spectroscopy. • Correlation between chemical structure and membrane separation performance. [ABSTRACT FROM AUTHOR]

We report here structure-property relationship between linear and branched polyethylene imines by examining their antimicrobial activities against wide range of pathogens. Both the polymers target the cytoplasmic membrane of bacteria and yeasts, eliciting rapid microbicidal properties. Using multiscale molecular dynamic simulations, we showed that, in both fully or partially protonated forms LPEI discriminates between mammalian and bacterial model membranes whereas BPEI lacks selectivity for both the model membranes. Simulation results suggest that LPEI forms weak complex with the zwitterionic lipids whereas the side chain amino groups of BPEI sequester the zwitterionic lipids by forming tight complex. Consistent with these observations, label-free cell impedance measurements, cell viability assays and high content analysis indicate that BPEI is cytotoxic to human epithelial and fibroblasts cells. Crosslinking of BPEI onto electrospun gelatin mats attenuate the cytotoxicity for fibroblasts while retaining the antimicrobial activity against Gram-positive and yeasts strains. PEI crosslinked gelatin mats elicit bactericidal activity by contact-mediated killing and durable to leaching for 7 days. The potent antimicrobial activity combined with enhanced selectivity of the crosslinked ES gelatin mats would expand the arsenel of biocides in the management of superficial skin infections. The contact-mediated microbicidal properties may avert antimicrobial resistance and expand the diversity of applications to prevent microbial contamination. Statement of Significance Current commercially available advanced wound dressings are either impregnated with metallic silver or silver salts which have side effects or may not avert antimicrobial resistance. In this article, we have used multidisciplinary approach comprising of computational, chemical and biological methods to understand the antimicrobial properties and biocompatibility of linear (LPEI) and branched (BPEI) polyethylenimines. We then applied this knowledge to develop dual purpose wound dressings containing these polymers, which encourages healing while maintain antimicrobial activity. In addition, the approach can be expanded to rationalize the antimicrobial vs. cytotoxicity of other cationic polymers and the method of crosslinking would enhance their potentials as biocides for advanced materials. [ABSTRACT FROM AUTHOR]